1. Field of the Invention
The present invention relates to a changeover valve and relates more particularly to a changeover valve to be connected between a water filter and a water supply device to control the direction of the flow of water for filtration through the water filter, or for rinsing or back-washing the water filter.
2. Description of the Prior Art
In a water supply system provided with a water filter, backwashing has been commonly used to remove dirts from the strainer or filter element of the water filter. To backwash through a water filter, a changeover valve (which may also be referred to as a switching valve) is often used to connect the water supply device such as a faucet, and the water filter. By means of a changeover valve, the flow of water from the supply device can be guided to pass through the water filter in a forward direction for filtration or in a backward direction through the water filter to remove dirts from the water filter.
A conventional changeover valve for a water filter commonly comprises a valve case which has a water intake connected to a water supply device, a first connecting port and a second connecting port respectively connected to an inlet port and an outlet port of the water filter, a water outlet to discharge therethrough the filtrate from said water filter, and a drain port to carry dirty water out of the valve. The valve also has a valve body operable by a mechanism in the valve case to change the position of the valve body and thereby to permit the flow of water from the water supply to be discharged through the water outlet or through the drain port. When the valve is rotated to a filtration position to permit the flow of water to be filtered through the water filter, the water from the water supply will pass through the water intake and the first connecting port of the valve, the inlet port of the water filter, the outlet port of the water filter, the second connecting port and the water outlet of the valve case. When the valve is rotated to a backwashing position to permit the flow of water to flow through the water filter in the backward direction in order to remove dirts from the strainer or filter element, the water from the water supply device will pass through the water intake and the second connecting port of the valve, the water outlet port of the water filter, the water inlet port of the water filter, the first connecting port and the drain port of the valve. Such conventional changeover valve is still not satisfactory in use because it can not eliminate two problems.
The first problem happens during backwashing. When the water flows through a water filter in a backward direction during backwashing, the dirts which are carried in the water tend to be stopped by the filter element and accumulate at the water intake port of the water filter. The dirts may then be carried by the water when the valve body is rotated to the filtration position and discharged with the filtered water through the water outlet port of the valve.
The second problem happens during filtration. When water passes through the water filter which has not been operated for a prolonged period of time, decayed organic matter in the residual water retained in the water filter may be carried by the filtrate from the water filter and discharged through the water outlet port of the valve.
Therefore, a water filter must be rinsed both before filtration and after backwashing. To rinse a water filter, the flow of water must be guided through the water filter in a forward direction so that dirts are carried out of the water filter. The changeover valve which connects the water supply device and the water filter should therefore have a drain port separated from the water outlet port thereof to discharge rinsing water so as to prevent possible contamination. A conventional changeover valve simply has a water outlet port for the discharge of flow of water out of the valve, therefore the filtered water may still contain dirts or decayed matter.